Techniques and apparatuses for ultra-reliable low-latency communications transmission using grant-free resources

ABSTRACT

Certain aspects of the present disclosure generally relate to wireless communication. In some aspects, a user equipment may transmit, and a base station may receive, on a grant-free resource, in an ultra-reliable low-latency communications (URLLC) network, a layer 1 (L1) signal for identification of the user equipment. In some aspects, the base station may transmit, and the user equipment may monitor for and receive a reception indication as a response to the L1 signal in a reception period occurring after transmission of the L1 signal. Numerous other aspects are provided.

CROSS-REFERENCE TO RELATED APPLICATIONS UNDER 35 U.S.C. § 119

This application claims priority to Provisional Patent Application No. 62/544,316, filed Aug. 11, 2017, entitled “TECHNIQUES AND APPARATUSES FOR ULTRA-RELIABLE LOW-LATENCY COMMUNICATIONS TRANSMISSION USING GRANT-FREE RESOURCES,” which is hereby expressly incorporated by reference herein.

FIELD OF THE DISCLOSURE

Aspects of the present disclosure generally relate to wireless communication, and more particularly to techniques and apparatuses for ultra-reliable low-latency communications (URLLC) transmission using grant-free resources.

BACKGROUND

Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasts. Typical wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power, etc.). Examples of such multiple-access technologies include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency-division multiple access (FDMA) systems, orthogonal frequency-division multiple access (OFDMA) systems, single-carrier frequency-division multiple access (SC-FDMA) systems, time division synchronous code division multiple access (TD-SCDMA) systems, and Long Term Evolution (LTE). LTE/LTE-Advanced is a set of enhancements to the Universal Mobile Telecommunications System (UMTS) mobile standard promulgated by the Third Generation Partnership Project (3GPP).

A wireless communication network may include a number of base stations (BSs) that can support communication for a number of user equipment (UEs). A user equipment (UE) may communicate with a base station (BS) via the downlink and uplink. The downlink (or forward link) refers to the communication link from the BS to the UE, and the uplink (or reverse link) refers to the communication link from the UE to the BS. As will be described in more detail herein, a BS may be referred to as a Node B, a gNB, an access point (AP), a radio head, a transmit receive point (TRP), a new radio (NR) BS, a 5G Node B, and/or the like.

The above multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different user equipment to communicate on a municipal, national, regional, and even global level. New radio (NR), which may also be referred to as 5G, is a set of enhancements to the LTE mobile standard promulgated by the Third Generation Partnership Project (3GPP). NR is designed to better support mobile broadband Internet access by improving spectral efficiency, lowering costs, improving services, making use of new spectrum, and better integrating with other open standards using orthogonal frequency division multiplexing (OFDM) with a cyclic prefix (CP) (CP-OFDM) on the downlink (DL), using CP-OFDM and/or SC-FDM (e.g., also known as discrete Fourier transform spread OFDM (DFT-s-OFDM)) on the uplink (UL), as well as supporting beamforming, multiple-input multiple-output (MIMO) antenna technology, and carrier aggregation. However, as the demand for mobile broadband access continues to increase, there exists a need for further improvements in LTE and NR technologies. Preferably, these improvements should be applicable to other multiple access technologies and the telecommunication standards that employ these technologies.

SUMMARY

In some aspects, a method for wireless communication performed by a user equipment (UE) may include transmitting, on a grant-free resource in an ultra-reliable low-latency communications (URLLC) network, data and a layer 1 (L1) signal for identification of the UE. The method may include monitoring for a reception indication as a response to the L1 signal in a reception period occurring after transmission of the L1 signal on the grant-free resource.

In some aspects, a user equipment (UE) for wireless communication may include a memory and one or more processors operatively coupled to the memory. The memory and the one or more processors may be configured to transmit, on a grant-free resource in an ultra-reliable low-latency communications (URLLC) network, data and a layer 1 (L1) signal for identification of the UE. The memory and the one or more processors may be configured to monitor for a reception indication as a response to the L1 signal in a reception period occurring after transmission of the L1 signal on the grant-free resource.

In some aspects, a non-transitory computer-readable medium may store one or more instructions for wireless communication. The one or more instructions, when executed by one or more processors of a user equipment (UE), may cause the one or more processors to transmit, on a grant-free resource in an ultra-reliable low-latency communications (URLLC) network, data and a layer 1 (L1) signal for identification of the UE. The one or more instructions, when executed by the one or more processors, may cause the one or more processors to monitor for a reception indication as a response to the L1 signal in a reception period occurring after transmission of the L1 signal on the grant-free resource.

In some aspects, an apparatus for wireless communication may include means for transmitting, on a grant-free resource in an ultra-reliable low-latency communications (URLLC) network, data and a layer 1 (L1) signal for identification of the apparatus. The apparatus may include means for monitoring for a reception indication as a response to the L1 signal in a reception period occurring after transmission of the L1 signal on the grant-free resource.

In some aspects, a method for wireless communication may include receiving, in an ultra-reliable low-latency communications (URLLC) network, a layer 1 (L1) signal on a grant-free resource. The method may include identifying a user equipment (UE) that transmitted on the grant-free resource based on the L1 signal. The method may include transmitting, to the UE, a reception indication as a response to the L1 signal in a reception period occurring after reception of the L1 signal.

In some aspects, a base station for wireless communication may include a memory and one or more processors operatively coupled to the memory. The memory and the one or more processors may be configured to receive, in an ultra-reliable low-latency communications (URLLC) network, a layer 1 (L1) signal on a grant-free resource. The memory and the one or more processors may be configured to identify a user equipment (UE) that transmitted on the grant-free resource based on the L1 signal. The memory and the one or more processors may be configured to transmit, to the UE, a reception indication as a response to the L1 signal in a reception period occurring after reception of the L1 signal.

In some aspects, a non-transitory computer-readable medium may store one or more instructions for wireless communication. The one or more instructions, when executed by one or more processors of a base station, may cause the one or more processors to receive, in an ultra-reliable low-latency communications (URLLC) network, a layer 1 (L1) signal on a grant-free resource. The one or more instructions, when executed by the one or more processors of the base station, may cause the one or more processors to transmit, to identify a user equipment (UE) that transmitted on the grant-free resource based on the L1 signal. The one or more instructions, when executed by the one or more processors of the base station, may cause the one or more processors to transmit, to the UE, a reception indication as a response to the L1 signal in a reception period occurring after reception of the L1 signal.

In some aspects, an apparatus for wireless communication may include means for receiving, in an ultra-reliable low-latency communications (URLLC) network, a layer 1 (L1) signal on a grant-free resource. The apparatus may include means for identifying a user equipment (UE) that transmitted on the grant-free resource based on the L1 signal. The apparatus may include means for transmitting, to the UE, a reception indication as a response to the L1 signal in a reception period occurring after reception of the L1 signal.

Aspects generally a method, apparatus, system, computer program product, non-transitory computer-readable medium, user equipment, base station, wireless communication device, and processing system as substantially described herein with reference to and as illustrated by the accompanying drawings and specification.

The foregoing has outlined rather broadly the features and technical advantages of examples according to the disclosure in order that the detailed description that follows may be better understood. Additional features and advantages will be described hereinafter. The conception and specific examples disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present disclosure. Such equivalent constructions do not depart from the scope of the appended claims. Characteristics of the concepts disclosed herein, both their organization and method of operation, together with associated advantages will be better understood from the following description when considered in connection with the accompanying figures. Each of the figures is provided for the purpose of illustration and description, and not as a definition of the limits of the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the present disclosure can be understood in detail, a more particular description, briefly summarized above, may be had by reference to aspects, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only certain typical aspects of this disclosure and are therefore not to be considered limiting of its scope, for the description may admit to other equally effective aspects. The same reference numbers in different drawings may identify the same or similar elements.

FIG. 1 is a block diagram conceptually illustrating an example of a wireless communication network, in accordance with various aspects of the present disclosure.

FIG. 2 is a block diagram conceptually illustrating an example of a base station in communication with a user equipment (UE) in a wireless communication network, in accordance with various aspects of the present disclosure.

FIG. 3 is a block diagram conceptually illustrating an example of a frame structure in a wireless communication network, in accordance with various aspects of the present disclosure.

FIG. 4 is a block diagram conceptually illustrating two example subframe formats with the normal cyclic prefix, in accordance with various aspects of the present disclosure.

FIG. 5 illustrates an example logical architecture of a distributed radio access network (RAN), in accordance with various aspects of the present disclosure.

FIG. 6 illustrates an example physical architecture of a distributed RAN, in accordance with various aspects of the present disclosure.

FIG. 7 is a diagram illustrating an example of a downlink (DL)-centric subframe, in accordance with various aspects of the present disclosure.

FIG. 8 is a diagram illustrating an example of an uplink (UL)-centric subframe, in accordance with various aspects of the present disclosure.

FIG. 9 is a diagram illustrating an example of ultra-reliable low-latency communications (URLLC) transmission using grant-free resources, in accordance with various aspects of the present disclosure.

FIG. 10 is a diagram illustrating an example of URLLC transmission using grant-free resources, in accordance with various aspects of the present disclosure.

FIG. 11 is a diagram illustrating an example process performed, for example, by a user equipment, in accordance with various aspects of the present disclosure.

FIG. 12 is a diagram illustrating an example process performed, for example, by a base station, in accordance with various aspects of the present disclosure.

DETAILED DESCRIPTION

Various aspects of the disclosure are described more fully hereinafter with reference to the accompanying drawings. This disclosure may, however, be embodied in many different forms and should not be construed as limited to any specific structure or function presented throughout this disclosure. Rather, these aspects are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Based at least in part on the teachings herein one skilled in the art should appreciate that the scope of the disclosure is intended to cover any aspect of the disclosure disclosed herein, whether implemented independently of or combined with any other aspect of the disclosure. For example, an apparatus may be implemented or a method may be practiced using any number of the aspects set forth herein. In addition, the scope of the disclosure is intended to cover such an apparatus or method which is practiced using other structure, functionality, or structure and functionality in addition to or other than the various aspects of the disclosure set forth herein. It should be understood that any aspect of the disclosure disclosed herein may be embodied by one or more elements of a claim.

Several aspects of telecommunication systems will now be presented with reference to various apparatuses and techniques. These apparatuses and techniques will be described in the following detailed description and illustrated in the accompanying drawings by various blocks, modules, components, circuits, steps, processes, algorithms, etc. (collectively referred to as “elements”). These elements may be implemented using hardware, software, or combinations thereof. Whether such elements are implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system.

It is noted that while aspects may be described herein using terminology commonly associated with 3G and/or 4G wireless technologies, aspects of the present disclosure can be applied in other generation-based communication systems, such as 5G and later, including NR technologies.

FIG. 1 is a diagram illustrating a network 100 in which aspects of the present disclosure may be practiced. The network 100 may be an LTE network or some other wireless network, such as a 5G or NR network. Wireless network 100 may include a number of BSs 110 (shown as BS 110 a, BS 110 b, BS 110 c, and BS 110 d) and other network entities. A BS is an entity that communicates with user equipment (UEs) and may also be referred to as a base station, a NR BS, a Node B, a gNB, a 5G node B (NB), an access point, a transmit receive point (TRP), and/or the like. Each BS may provide communication coverage for a particular geographic area. In 3GPP, the term “cell” can refer to a coverage area of a BS and/or a BS subsystem serving this coverage area, depending on the context in which the term is used.

A BS may provide communication coverage for a macro cell, a pico cell, a femto cell, and/or another type of cell. A macro cell may cover a relatively large geographic area (e.g., several kilometers in radius) and may allow unrestricted access by UEs with service subscription. A pico cell may cover a relatively small geographic area and may allow unrestricted access by UEs with service subscription. A femto cell may cover a relatively small geographic area (e.g., a home) and may allow restricted access by UEs having association with the femto cell (e.g., UEs in a closed subscriber group (CSG)). A BS for a macro cell may be referred to as a macro BS. A BS for a pico cell may be referred to as a pico BS. A BS for a femto cell may be referred to as a femto BS or a home BS. In the example shown in FIG. 1, a BS 110 a may be a macro BS for a macro cell 102 a, a BS 110 b may be a pico BS for a pico cell 102 b, and a BS 110 c may be a femto BS for a femto cell 102 c. A BS may support one or multiple (e.g., three) cells. The terms “eNB”, “base station”, “NR BS”, “gNB”, “TRP”, “AP”, “node B”, “5G NB”, and “cell” may be used interchangeably herein.

In some examples, a cell may not necessarily be stationary, and the geographic area of the cell may move according to the location of a mobile BS. In some examples, the BSs may be interconnected to one another and/or to one or more other BSs or network nodes (not shown) in the access network 100 through various types of backhaul interfaces such as a direct physical connection, a virtual network, and/or the like using any suitable transport network.

Wireless network 100 may also include relay stations. A relay station is an entity that can receive a transmission of data from an upstream station (e.g., a BS or a UE) and send a transmission of the data to a downstream station (e.g., a UE or a BS). A relay station may also be a UE that can relay transmissions for other UEs. In the example shown in FIG. 1, a relay station 110 d may communicate with macro BS 110 a and a UE 120 d in order to facilitate communication between BS 110 a and UE 120 d. A relay station may also be referred to as a relay BS, a relay base station, a relay, etc.

Wireless network 100 may be a heterogeneous network that includes BSs of different types, e.g., macro BSs, pico BSs, femto BSs, relay BSs, etc. These different types of BSs may have different transmit power levels, different coverage areas, and different impact on interference in wireless network 100. For example, macro BSs may have a high transmit power level (e.g., 5 to 40 Watts) whereas pico BSs, femto BSs, and relay BSs may have lower transmit power levels (e.g., 0.1 to 2 Watts).

A network controller 130 may couple to a set of BSs and may provide coordination and control for these BSs. Network controller 130 may communicate with the BSs via a backhaul. The BSs may also communicate with one another, e.g., directly or indirectly via a wireless or wireline backhaul.

UEs 120 (e.g., 120 a, 120 b, 120 c) may be dispersed throughout wireless network 100, and each UE may be stationary or mobile. A UE may also be referred to as an access terminal, a terminal, a mobile station, a subscriber unit, a station, etc. A UE may be a cellular phone (e.g., a smart phone), a personal digital assistant (PDA), a wireless modem, a wireless communication device, a handheld device, a laptop computer, a cordless phone, a wireless local loop (WLL) station, a tablet, a camera, a gaming device, a netbook, a smartbook, an ultrabook, medical device or equipment, biometric sensors/devices, wearable devices (smart watches, smart clothing, smart glasses, smart wrist bands, smart jewelry (e.g., smart ring, smart bracelet)), an entertainment device (e.g., a music or video device, or a satellite radio), a vehicular component or sensor, smart meters/sensors, industrial manufacturing equipment, a global positioning system device, or any other suitable device that is configured to communicate via a wireless or wired medium.

Some UEs may be considered machine-type communication (MTC) or evolved or enhanced machine-type communication (eMTC) UEs. MTC and eMTC UEs include, for example, robots, drones, remote devices, such as sensors, meters, monitors, location tags, etc., that may communicate with a base station, another device (e.g., remote device), or some other entity. A wireless node may provide, for example, connectivity for or to a network (e.g., a wide area network such as Internet or a cellular network) via a wired or wireless communication link. Some UEs may be considered Internet-of-Things (IoT) devices, and/or may be implemented as may be implemented as NB-IoT (narrowband internet of things) devices. Some UEs may be considered a Customer Premises Equipment (CPE). UE 120 may be included inside a housing that houses components of UE 120, such as processor components, memory components, and/or the like.

In general, any number of wireless networks may be deployed in a given geographic area. Each wireless network may support a particular RAT and may operate on one or more frequencies. A RAT may also be referred to as a radio technology, an air interface, etc. A frequency may also be referred to as a carrier, a frequency channel, etc. Each frequency may support a single RAT in a given geographic area in order to avoid interference between wireless networks of different RATs. In some cases, NR or 5G RAT networks may be deployed.

In some examples, access to the air interface may be scheduled, wherein a scheduling entity (e.g., a base station) allocates resources for communication among some or all devices and equipment within the scheduling entity's service area or cell. Within the present disclosure, as discussed further below, the scheduling entity may be responsible for scheduling, assigning, reconfiguring, and releasing resources for one or more subordinate entities. That is, for scheduled communication, subordinate entities utilize resources allocated by the scheduling entity.

Base stations are not the only entities that may function as a scheduling entity. That is, in some examples, a UE may function as a scheduling entity, scheduling resources for one or more subordinate entities (e.g., one or more other UEs). In this example, the UE is functioning as a scheduling entity, and other UEs utilize resources scheduled by the UE for wireless communication. A UE may function as a scheduling entity in a peer-to-peer (P2P) network, and/or in a mesh network. In a mesh network example, UEs may optionally communicate directly with one another in addition to communicating with the scheduling entity.

Thus, in a wireless communication network with a scheduled access to time-frequency resources and having a cellular configuration, a P2P configuration, and a mesh configuration, a scheduling entity and one or more subordinate entities may communicate utilizing the scheduled resources.

As indicated above, FIG. 1 is provided merely as an example. Other examples are possible and may differ from what was described with regard to FIG. 1.

FIG. 2 shows a block diagram of a design 200 of base station 110 and UE 120, which may be one of the base stations and one of the UEs in FIG. 1. Base station 110 may be equipped with T antennas 234 a through 234 t, and UE 120 may be equipped with R antennas 252 a through 252 r, where in general T≥1 and R≥1.

At base station 110, a transmit processor 220 may receive data from a data source 212 for one or more UEs, select one or more modulation and coding schemes (MCS) for each UE based at least in part on channel quality indicators (CQIs) received from the UE, process (e.g., encode and modulate) the data for each UE based at least in part on the MCS(s) selected for the UE, and provide data symbols for all UEs. Transmit processor 220 may also process system information (e.g., for semi-static resource partitioning information (SRPI), etc.) and control information (e.g., CQI requests, grants, upper layer signaling, etc.) and provide overhead symbols and control symbols. Transmit processor 220 may also generate reference symbols for reference signals (e.g., the cell-specific reference signal (CRS)) and synchronization signals (e.g., the primary synchronization signal (PSS) and secondary synchronization signal (SSS)). A transmit (TX) multiple-input multiple-output (MIMO) processor 230 may perform spatial processing (e.g., precoding) on the data symbols, the control symbols, the overhead symbols, and/or the reference symbols, if applicable, and may provide T output symbol streams to T modulators (MODs) 232 a through 232 t. Each modulator 232 may process a respective output symbol stream (e.g., for OFDM, etc.) to obtain an output sample stream. Each modulator 232 may further process (e.g., convert to analog, amplify, filter, and upconvert) the output sample stream to obtain a downlink signal. T downlink signals from modulators 232 a through 232 t may be transmitted via T antennas 234 a through 234 t, respectively. According to certain aspects described in more detail below, the synchronization signals can be generated with location encoding to convey additional information.

At UE 120, antennas 252 a through 252 r may receive the downlink signals from base station 110 and/or other base stations and may provide received signals to demodulators (DEMODs) 254 a through 254 r, respectively. Each demodulator 254 may condition (e.g., filter, amplify, downconvert, and digitize) a received signal to obtain input samples. Each demodulator 254 may further process the input samples (e.g., for OFDM, etc.) to obtain received symbols. A MIMO detector 256 may obtain received symbols from all R demodulators 254 a through 254 r, perform MIMO detection on the received symbols if applicable, and provide detected symbols. A receive processor 258 may process (e.g., demodulate and decode) the detected symbols, provide decoded data for UE 120 to a data sink 260, and provide decoded control information and system information to a controller/processor 280. A channel processor may determine reference signal received power (RSRP), received signal strength indicator (RSSI), reference signal received quality (RSRQ), channel quality indicator (CQI), etc.

On the uplink, at UE 120, a transmit processor 264 may receive and process data from a data source 262 and control information (e.g., for reports comprising RSRP, RSSI, RSRQ, CQI, etc.) from controller/processor 280. Transmit processor 264 may also generate reference symbols for one or more reference signals. The symbols from transmit processor 264 may be precoded by a TX MIMO processor 266 if applicable, further processed by modulators 254 a through 254 r (e.g., for DFT-s-OFDM, CP-OFDM, etc.), and transmitted to base station 110. At base station 110, the uplink signals from UE 120 and other UEs may be received by antennas 234, processed by demodulators 232, detected by a MIMO detector 236 if applicable, and further processed by a receive processor 238 to obtain decoded data and control information sent by UE 120. Receive processor 238 may provide the decoded data to a data sink 239 and the decoded control information to controller/processor 240. Base station 110 may include communication unit 244 and communicate to network controller 130 via communication unit 244. Network controller 130 may include communication unit 294, controller/processor 290, and memory 292.

In some aspects, one or more components of UE 120 may be included in a housing. Controller/processor 240 of base station 110, controller/processor 280 of UE 120, and/or any other component(s) of FIG. 2 may perform one or more techniques associated with ultra-reliable low-latency communications (URLLC) transmission using grant-free resources, as described in more detail elsewhere herein. For example, controller/processor 240 of base station 110, controller/processor 280 of UE 120, and/or any other component(s) of FIG. 2 may perform or direct operations of, for example, process 1100 of FIG. 11, process 1200 of FIG. 12, and/or other processes as described herein. Memories 242 and 282 may store data and program codes for base station 110 and UE 120, respectively. A scheduler 246 may schedule UEs for data transmission on the downlink and/or uplink.

In some aspects, BS 110 may include means for receiving, in an ultra-reliable low-latency communications (URLLC) network, a layer 1 (L1) signal on a grant-free resource; means for identifying a user equipment (UE) that transmitted on the grant-free resource based on the L1 signal; means for transmitting, to the UE, a reception indication as a response to the L1 signal in a reception period occurring after reception of the L1 signal; and/or the like. In some aspects, such means may include one or more components of BS 110 described in connection with FIG. 2

In some aspects, UE 120 may include means for transmitting, on a grant-free resource in an ultra-reliable low-latency communications (URLLC) network, data and a layer 1 (L1) signal for identification of the UE; means for monitoring for a reception indication as a response to the L1 signal in a reception period occurring after transmission of the L1 signal on the grant-free resource; and/or the like. In some aspects, such means may include one or more components of UE 120 described in connection with FIG. 2.

As indicated above, FIG. 2 is provided merely as an example. Other examples are possible and may differ from what was described with regard to FIG. 2.

FIG. 3 shows an example frame structure 300 for frequency division duplexing (FDD) in a telecommunications system (e.g., LTE). The transmission timeline for each of the downlink and uplink may be partitioned into units of radio frames. Each radio frame may have a predetermined duration (e.g., 10 milliseconds (ms)) and may be partitioned into 10 subframes with indices of 0 through 9. Each subframe may include two slots. Each radio frame may thus include 20 slots with indices of 0 through 19. Each slot may include L symbol periods, e.g., seven symbol periods for a normal cyclic prefix (as shown in FIG. 3) or six symbol periods for an extended cyclic prefix. The 2L symbol periods in each subframe may be assigned indices of 0 through 2L−1.

While some techniques are described herein in connection with frames, subframes, slots, and/or the like, these techniques may equally apply to other types of wireless communication structures, which may be referred to using terms other than “frame,” “subframe,” “slot,” and/or the like in 5G NR. In some aspects, a wireless communication structure may refer to a periodic time-bounded communication unit defined by a wireless communication standard and/or protocol.

In certain telecommunications (e.g., LTE), a BS may transmit a primary synchronization signal (PSS) and a secondary synchronization signal (SSS) on the downlink in the center of the system bandwidth for each cell supported by the BS. The PSS and SSS may be transmitted in symbol periods 6 and 5, respectively, in subframes 0 and 5 of each radio frame with the normal cyclic prefix, as shown in FIG. 3. The PSS and SSS may be used by UEs for cell search and acquisition. The BS may transmit a cell-specific reference signal (CRS) across the system bandwidth for each cell supported by the BS. The CRS may be transmitted in certain symbol periods of each subframe and may be used by the UEs to perform channel estimation, channel quality measurement, and/or other functions. The BS may also transmit a physical broadcast channel (PBCH) in symbol periods 0 to 3 in slot 1 of certain radio frames. The PBCH may carry some system information. The BS may transmit other system information such as system information blocks (SIBs) on a physical downlink shared channel (PDSCH) in certain subframes. The BS may transmit control information/data on a physical downlink control channel (PDCCH) in the first B symbol periods of a subframe, where B may be configurable for each subframe. The BS may transmit traffic data and/or other data on the PDSCH in the remaining symbol periods of each subframe.

In other systems (e.g., such NR or 5G systems), a Node B may transmit these or other signals in these locations or in different locations of the subframe.

As indicated above, FIG. 3 is provided merely as an example. Other examples are possible and may differ from what was described with regard to FIG. 3.

FIG. 4 shows two example subframe formats 410 and 420 with the normal cyclic prefix. The available time frequency resources may be partitioned into resource blocks. Each resource block may cover 12 subcarriers in one slot and may include a number of resource elements. Each resource element may cover one subcarrier in one symbol period and may be used to send one modulation symbol, which may be a real or complex value.

Subframe format 410 may be used for two antennas. A CRS may be transmitted from antennas 0 and 1 in symbol periods 0, 4, 7, and 11. A reference signal is a signal that is known a priori by a transmitter and a receiver and may also be referred to as a pilot signal. A CRS is a reference signal that is specific for a cell, e.g., generated based at least in part on a cell identity (ID). In FIG. 4, for a given resource element with label Ra, a modulation symbol may be transmitted on that resource element from antenna a, and no modulation symbols may be transmitted on that resource element from other antennas. Subframe format 420 may be used with four antennas. A CRS may be transmitted from antennas 0 and 1 in symbol periods 0, 4, 7, and 11 and from antennas 2 and 3 in symbol periods 1 and 8. For both subframe formats 410 and 420, a CRS may be transmitted on evenly spaced subcarriers, which may be determined based at least in part on cell ID. CRSs may be transmitted on the same or different subcarriers, depending on their cell IDs. For both subframe formats 410 and 420, resource elements not used for the CRS may be used to transmit data (e.g., traffic data, control data, and/or other data).

The PSS, SSS, CRS and PBCH in LTE are described in 3GPP Technical Specification (TS) 36.211, entitled “Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channels and Modulation,” which is publicly available.

An interlace structure may be used for each of the downlink and uplink for FDD in certain telecommunications systems (e.g., LTE). For example, Q interlaces with indices of 0 through Q−1 may be defined, where Q may be equal to 4, 6, 8, 10, or some other value. Each interlace may include subframes that are spaced apart by Q frames. In particular, interlace q may include subframes q, q+Q, q+2Q, etc., where q ∈{0, . . . , Q−1}.

The wireless network may support hybrid automatic retransmission request (HARQ) for data transmission on the downlink and uplink. For HARQ, a transmitter (e.g., a BS) may send one or more transmissions of a packet until the packet is decoded correctly by a receiver (e.g., a UE) or some other termination condition is encountered. For synchronous HARQ, all transmissions of the packet may be sent in subframes of a single interlace. For asynchronous HARQ, each transmission of the packet may be sent in any subframe.

A UE may be located within the coverage of multiple BSs. One of these BSs may be selected to serve the UE. The serving BS may be selected based at least in part on various criteria such as received signal strength, received signal quality, path loss, and/or the like. Received signal quality may be quantified by a signal-to-noise-and-interference ratio (SINR), or a reference signal received quality (RSRQ), or some other metric. The UE may operate in a dominant interference scenario in which the UE may observe high interference from one or more interfering BSs.

While aspects of the examples described herein may be associated with LTE technologies, aspects of the present disclosure may be applicable with other wireless communication systems, such as NR or 5G technologies.

New radio (NR) may refer to radios configured to operate according to a new air interface (e.g., other than Orthogonal Frequency Divisional Multiple Access (OFDMA)-based air interfaces) or fixed transport layer (e.g., other than Internet Protocol (IP)). In aspects, NR may utilize OFDM with a CP (herein referred to as cyclic prefix OFDM or CP-OFDM) and/or SC-FDM on the uplink, may utilize CP-OFDM on the downlink and include support for half-duplex operation using time division duplexing (TDD). In aspects, NR may, for example, utilize OFDM with a CP (herein referred to as CP-OFDM) and/or discrete Fourier transform spread orthogonal frequency-division multiplexing (DFT-s-OFDM) on the uplink, may utilize CP-OFDM on the downlink and include support for half-duplex operation using TDD. NR may include Enhanced Mobile Broadband (eMBB) service targeting wide bandwidth (e.g., 80 megahertz (MHz) and beyond), millimeter wave (mmW) targeting high carrier frequency (e.g., 60 gigahertz (GHz)), massive MTC (mMTC) targeting non-backward compatible MTC techniques, and/or mission critical targeting ultra reliable low latency communications (URLLC) service.

A single component carrier bandwidth of 100 MHZ may be supported. NR resource blocks may span 12 sub-carriers with a sub-carrier bandwidth of 75 kilohertz (kHz) over a 0.1 ms duration. Each radio frame may include 50 subframes with a length of 10 ms. Consequently, each subframe may have a length of 0.2 ms. Each subframe may indicate a link direction (e.g., DL or UL) for data transmission and the link direction for each subframe may be dynamically switched. Each subframe may include downlink/uplink (DL/UL) data as well as DL/UL control data.

Beamforming may be supported and beam direction may be dynamically configured. MIMO transmissions with precoding may also be supported. MIMO configurations in the DL may support up to 8 transmit antennas with multi-layer DL transmissions up to 8 streams and up to 2 streams per UE. Multi-layer transmissions with up to 2 streams per UE may be supported. Aggregation of multiple cells may be supported with up to 8 serving cells. Alternatively, NR may support a different air interface, other than an OFDM-based interface. NR networks may include entities such central units or distributed units.

The RAN may include a central unit (CU) and distributed units (DUs). A NR BS (e.g., gNB, 5G Node B, Node B, transmit receive point (TRP), access point (AP)) may correspond to one or multiple BSs. NR cells can be configured as access cells (ACells) or data only cells (DCells). For example, the RAN (e.g., a central unit or distributed unit) can configure the cells. DCells may be cells used for carrier aggregation or dual connectivity, but not used for initial access, cell selection/reselection, or handover. In some cases, DCells may not transmit synchronization signals. In some cases, DCells may transmit synchronization signals. NR BSs may transmit downlink signals to UEs indicating the cell type. Based at least in part on the cell type indication, the UE may communicate with the NR BS. For example, the UE may determine NR BSs to consider for cell selection, access, handover, and/or measurement based at least in part on the indicated cell type.

As indicated above, FIG. 4 is provided merely as an example. Other examples are possible and may differ from what was described with regard to FIG. 4.

FIG. 5 illustrates an example logical architecture of a distributed RAN 500, according to aspects of the present disclosure. A 5G access node 506 may include an access node controller (ANC) 502. The ANC may be a central unit (CU) of the distributed RAN 500. The backhaul interface to the next generation core network (NG-CN) 504 may terminate at the ANC. The backhaul interface to neighboring next generation access nodes (NG-ANs) may terminate at the ANC. The ANC may include one or more TRPs 508 (which may also be referred to as BSs, NR BSs, Node Bs, 5G NBs, APs, gNB, or some other term). As described above, a TRP may be used interchangeably with “cell.”

The TRPs 508 may be a distributed unit (DU). The TRPs may be connected to one ANC (ANC 502) or more than one ANC (not illustrated). For example, for RAN sharing, radio as a service (RaaS), and service specific AND deployments, the TRP may be connected to more than one ANC. A TRP may include one or more antenna ports. The TRPs may be configured to individually (e.g., dynamic selection) or jointly (e.g., joint transmission) serve traffic to a UE.

The local architecture of RAN 500 may be used to illustrate fronthaul definition. The architecture may be defined that support fronthauling solutions across different deployment types. For example, the architecture may be based at least in part on transmit network capabilities (e.g., bandwidth, latency, and/or jitter).

The architecture may share features and/or components with LTE. According to aspects, the next generation AN (NG-AN) 510 may support dual connectivity with NR. The NG-AN may share a common fronthaul for LTE and NR.

The architecture may enable cooperation between and among TRPs 508. For example, cooperation may be preset within a TRP and/or across TRPs via the ANC 502. According to aspects, no inter-TRP interface may be needed/present.

According to aspects, a dynamic configuration of split logical functions may be present within the architecture of RAN 500. The packet data convergence protocol (PDCP), radio link control (RLC), media access control (MAC) protocol may be adaptably placed at the ANC or TRP.

According to certain aspects, a BS may include a central unit (CU) (e.g., ANC 502) and/or one or more distributed units (e.g., one or more TRPs 508).

As indicated above, FIG. 5 is provided merely as an example. Other examples are possible and may differ from what was described with regard to FIG. 5.

FIG. 6 illustrates an example physical architecture of a distributed RAN 600, according to aspects of the present disclosure. A centralized core network unit (C-CU) 602 may host core network functions. The C-CU may be centrally deployed. C-CU functionality may be offloaded (e.g., to advanced wireless services (AWS)), in an effort to handle peak capacity.

A centralized RAN unit (C-RU) 604 may host one or more ANC functions. Optionally, the C-RU may host core network functions locally. The C-RU may have distributed deployment. The C-RU may be closer to the network edge.

A distributed unit (DU) 606 may host one or more TRPs. The DU may be located at edges of the network with radio frequency (RF) functionality.

As indicated above, FIG. 6 is provided merely as an example. Other examples are possible and may differ from what was described with regard to FIG. 6.

FIG. 7 is a diagram 700 showing an example of a DL-centric subframe or wireless communication structure. The DL-centric subframe may include a control portion 702. The control portion 702 may exist in the initial or beginning portion of the DL-centric subframe. The control portion 702 may include various scheduling information and/or control information corresponding to various portions of the DL-centric subframe. In some configurations, the control portion 702 may be a physical DL control channel (PDCCH), as indicated in FIG. 7. In some aspects, the control portion 702 may include legacy PDCCH information, shortened PDCCH (sPDCCH) information), a control format indicator (CFI) value (e.g., carried on a physical control format indicator channel (PCFICH)), one or more grants (e.g., downlink grants, uplink grants, etc.), and/or the like.

The DL-centric subframe may also include a DL data portion 704. The DL data portion 704 may sometimes be referred to as the payload of the DL-centric subframe. The DL data portion 704 may include the communication resources utilized to communicate DL data from the scheduling entity (e.g., UE or BS) to the subordinate entity (e.g., UE). In some configurations, the DL data portion 704 may be a physical DL shared channel (PDSCH).

The DL-centric subframe may also include an UL short burst portion 706. The UL short burst portion 706 may sometimes be referred to as an UL burst, an UL burst portion, a common UL burst, a short burst, an UL short burst, a common UL short burst, a common UL short burst portion, and/or various other suitable terms. In some aspects, the UL short burst portion 706 may include one or more reference signals. Additionally, or alternatively, the UL short burst portion 706 may include feedback information corresponding to various other portions of the DL-centric subframe. For example, the UL short burst portion 706 may include feedback information corresponding to the control portion 702 and/or the data portion 704. Non-limiting examples of information that may be included in the UL short burst portion 706 include an ACK signal (e.g., a PUCCH ACK, a PUSCH ACK, an immediate ACK), a NACK signal (e.g., a PUCCH NACK, a PUSCH NACK, an immediate NACK), a scheduling request (SR), a buffer status report (BSR), a HARQ indicator, a channel state indication (CSI), a channel quality indicator (CQI), a sounding reference signal (SRS), a demodulation reference signal (DMRS), PUSCH data, and/or various other suitable types of information. The UL short burst portion 706 may include additional or alternative information, such as information pertaining to random access channel (RACH) procedures, scheduling requests, and various other suitable types of information.

As illustrated in FIG. 7, the end of the DL data portion 704 may be separated in time from the beginning of the UL short burst portion 706. This time separation may sometimes be referred to as a gap, a guard period, a guard interval, and/or various other suitable terms. This separation provides time for the switch-over from DL communication (e.g., reception operation by the subordinate entity (e.g., UE)) to UL communication (e.g., transmission by the subordinate entity (e.g., UE)). The foregoing is merely one example of a DL-centric wireless communication structure, and alternative structures having similar features may exist without necessarily deviating from the aspects described herein.

As indicated above, FIG. 7 is provided merely as an example. Other examples are possible and may differ from what was described with regard to FIG. 7.

FIG. 8 is a diagram 800 showing an example of an UL-centric subframe or wireless communication structure. The UL-centric subframe may include a control portion 802. The control portion 802 may exist in the initial or beginning portion of the UL-centric subframe. The control portion 802 in FIG. 8 may be similar to the control portion 702 described above with reference to FIG. 7. The UL-centric subframe may also include an UL long burst portion 804. The UL long burst portion 804 may sometimes be referred to as the payload of the UL-centric subframe. The UL portion may refer to the communication resources utilized to communicate UL data from the subordinate entity (e.g., UE) to the scheduling entity (e.g., UE or BS). In some configurations, the control portion 802 may be a physical DL control channel (PDCCH).

As illustrated in FIG. 8, the end of the control portion 802 may be separated in time from the beginning of the UL long burst portion 804. This time separation may sometimes be referred to as a gap, guard period, guard interval, and/or various other suitable terms. This separation provides time for the switch-over from DL communication (e.g., reception operation by the scheduling entity) to UL communication (e.g., transmission by the scheduling entity).

The UL-centric subframe may also include an UL short burst portion 806. The UL short burst portion 806 in FIG. 8 may be similar to the UL short burst portion 706 described above with reference to FIG. 7, and may include any of the information described above in connection with FIG. 7. The foregoing is merely one example of an UL-centric wireless communication structure, and alternative structures having similar features may exist without necessarily deviating from the aspects described herein.

In some circumstances, two or more subordinate entities (e.g., UEs) may communicate with each other using sidelink signals. Real-world applications of such sidelink communications may include public safety, proximity services, UE-to-network relaying, vehicle-to-vehicle (V2V) communications, Internet of Everything (IoE) communications, IoT communications, mission-critical mesh, and/or various other suitable applications. Generally, a sidelink signal may refer to a signal communicated from one subordinate entity (e.g., UE1) to another subordinate entity (e.g., UE2) without relaying that communication through the scheduling entity (e.g., UE or BS), even though the scheduling entity may be utilized for scheduling and/or control purposes. In some examples, the sidelink signals may be communicated using a licensed spectrum (unlike wireless local area networks, which typically use an unlicensed spectrum).

In one example, a wireless communication structure, such as a frame, may include both UL-centric subframes and DL-centric subframes. In this example, the ratio of UL-centric subframes to DL-centric subframes in a frame may be dynamically adjusted based at least in part on the amount of UL data and the amount of DL data that are transmitted. For example, if there is more UL data, then the ratio of UL-centric subframes to DL-centric subframes may be increased. Conversely, if there is more DL data, then the ratio of UL-centric subframes to DL-centric subframes may be decreased.

As indicated above, FIG. 8 is provided merely as an example. Other examples are possible and may differ from what was described with regard to FIG. 8.

In certain communication systems (e.g., NR), a UE may transmit data using a preconfigured resource and without receiving an uplink grant. For example, the UE may transmit data to a BS. The UE may transmit a layer 1 (L1) signal, which may be used for collision avoidance, in connection with the data. The L1 signal may be a scheduling request (SR), a scrambled demodulation reference signal (DMRS), and/or the like. In some cases, a BS may receive the L1 signal, but may fail to receive the transmitted data as a result of the L1 signal being more resilient to collisions than the transmitted data. This may enable the BS to identify the UE in an interference limited scenario, when a threshold quantity of UEs are transmitting, and/or the like. In some other cases, the BS may fail to receive the L1 signal, which may cause the BS to be unable to determine whether a UE transmitted data if the data is not received, or, if the data is received, which UE transmitted the data. In URLLC, data may be transmitted in a single transmission and L1 signals may be less reliable than in other communication systems, thereby increasing a likelihood that a BS fails to receive an L1 signal and/or a data transmission from a UE.

If the transmitted data and the L1 signal are successfully received and there is no further data transmission for the BS to schedule, the BS may take no further action with regard to the UE. However, similarly, if the L1 signal is not successfully received, the BS may take no further action with regard to the UE as a result of being unable to determine which UE transmitted the data (if the data is successfully received) or as a result of lacking awareness that data was transmitted (if the data is not successfully received). When the UE does not receive an uplink grant for a new transmission or a retransmission during a reception period, the UE may incorrectly determine that the transmitted data and the L1 signal were successfully received, and may fail to retransmit the data.

Some aspects, described herein, may enable a UE to monitor for a reception indication as a response to an L1 signal after transmitting the L1 signal, thereby enabling the UE to correctly determine whether transmitted data was successfully received by a BS. For example, a UE may transmit an L1 signal to the BS in connection with data transmitted to the BS, and may monitor for a reception indication. If the BS successfully receives the L1 signal, the BS may provide and the UE may receive the reception indication during a reception period succeeding transmission of the L1 signal. In this case, the UE may correctly determine that the data was successfully received by the BS. Alternatively, if the BS does not successfully receive the L1 signal and does not provide the reception indication, the UE may determine that the L1 signal was not successfully received, and may retransmit the data and the L1 signal during a next available resource. In this way, a likelihood that a data transmission from a UE fails and is not retransmitted by the UE is reduced. Moreover, a latency of a retransmission of the data is reduced relative to another technique that does not schedule retransmission as a response to not receiving a reception indication.

FIG. 9 is a diagram illustrating an example 900 of URLLC transmission using grant-free resources. As shown in FIG. 9, example 900 includes a BS 110 and a UE 120.

As further shown in FIG. 9, and by reference number 905, UE 120 may transmit data and an L1 signal to BS 110. For example, UE 120 may transmit the data and the L1 signal using a grant-free resource (e.g., a preconfigured resource for UE 120). In some aspects, UE 120 may transmit the L1 signal in connection with the data for identification of UE 120. For example, UE 120 may transmit a scheduling request or a scrambled demodulation reference signal that identifies UE 120. In this case, the L1 signal may enable BS 110 to identify UE 120 as the UE, of a group of UEs in communication with BS 110, that transmitted the data.

In some aspects, based at least in part on transmitting the L1 signal, UE 120 may determine a reception period for receiving a reception indication from BS 110. For example, UE 120 may determine a reception period of at least one slot in which to receive the reception indication. In some aspects, the reception period may be a monitoring occasion immediately succeeding transmission of the L1 signal. During the reception period, in some aspects, UE 120 may attempt to receive (e.g., monitor for) the reception indication. For example, UE 120 may monitor a PDCCH to attempt to receive the reception indication. In some aspects, UE 120 may set a retransmission timer based at least in part on transmitting the L1 signal and the data. For example, when UE 120 fails to receive an uplink grant during the retransmission timer, UE 120 may determine that the data was successfully decoded by BS 110.

As further shown in FIG. 9, and by reference number 910, based at least in part on receiving the L1 signal, BS 110 may provide the reception indication, and UE 120 may receive the reception indication. For example, when monitoring a PDCCH to attempt to receive the reception indication during the reception period, UE 120 may receive the reception indication from BS 110. In this case, UE 120 may receive the reception indication in a first available PDCCH occasion occurring after BS 110 received the reception indication. In some aspects, BS 110 may transmit the L1 signal before completion of data decoding of the data. For example, BS 110 may receive the L1 signal, and may transmit the reception indication to UE 120 before completion of data decoding to reduce latency in providing the reception indication, thereby reducing a likelihood that UE 120 does not receive the reception indication during the reception period and retransmits the data. In this way, an amount of network traffic is reduced relative to another technique where UE 120 is more likely to retransmit the data.

In some aspects, UE 120 may receive the reception indication in an empty grant. For example, BS 110 may generate and transmit an empty grant message, and UE 120 may receive the empty grant message. In this way, the reception indication can be implemented without another downlink control information (DCI) message being specified for and supported by BS 110 and UE 120, thereby improving backwards compatibility relative to another technique that requires dedicated signaling to be specified and supported. In some aspects, UE 120 may attempt to receive the reception indication and may receive the reception indication based at least in part on a network configuration. For example, BS 110 may configure a URLLC network for providing reception indications based at least in part on determining that UE 120 supports receiving the reception indication, based at least in part on determining that a reliability of L1 signals in the network does not satisfy a URLLC reliability requirement (e.g., based at least in part on a signal strength, a quantity of UEs in the network, a level of interference, and/or the like), and/or the like.

In some aspects, BS 110 may provide and UE 120 may receive a configuration of grant-free resources that includes an indicator indicating whether or not the reception indicator is used for transmission of the configured resources. For example, UE 120 may receive an RRC message identifying grant-free resources for URLLC and indicating that a reception indicator is used with transmissions on the configured resources. In this case, UE 120 may monitor for the reception indicator in a next PDCCH occasion based at least in part on the RRC message. Alternatively, if the RRC message does not indicate that the reception indicator is used with transmissions on the configured resources, then UE 120 may use a timer to determine whether to retransmit.

As further shown in FIG. 9, and by reference number 915, in some aspects, UE 120 may receive an uplink (UL) grant. For example, based at least in part on BS 110 failing to successfully decode the data transmitted by UE 120, BS 110 may provide the uplink grant to enable UE 120 to retransmit the data to provide BS 110 another attempt to decode the data. As shown by reference number 920, in some aspects, based at least in part on receiving the uplink grant, UE 120 may retransmit the data and another L1 signal using the uplink grant.

As indicated above, FIG. 9 is provided as an example. Other examples are possible and may differ from what was described with respect to FIG. 9.

FIG. 10 is a diagram illustrating an example 1000 of URLLC transmission using grant-free resources, in accordance with various aspects of the present disclosure. As shown in FIG. 10, example 1000 includes a BS 110 and a UE 120.

As further shown in FIG. 10, and by reference number 1005, UE 120 may transmit data and an L1 signal to BS 110. For example, UE 120 may transmit the data and the L1 signal using a grant-free resource (e.g., a preconfigured resource for UE 120). As shown by reference number 1010, UE 120 may attempt to receive (e.g., monitor for) a reception indication from BS 110. For example, for a reception period of one slot, UE 120 may attempt to receive the reception indication. In this case, UE 120 does not receive the reception indication during the reception period. For example, based at least in part on BS 110 failing to receive or decode the L1 signal, BS 110 may not provide the reception indication and UE 120 may not receive the reception indication. In some aspects, BS 110 may receive and decode the L1 signal and provide the reception indication, and UE 120 may fail to receive or decode the reception indication (e.g., as a result of interference, signal degradation, and/or the like).

As further shown in FIG. 10, and by reference number 1015, UE 120 may retransmit the L1 signal and the data. For example, based at least in part on failing to receive or decode the reception indication during the reception period, UE 120 may retransmit the L1 signal and the data. In some aspects, UE 120 may retransmit the L1 signal and the data in a next available resource after the reception period. For example, during a next available grant-free resource preconfigured for UE 120, UE 120 may retransmit the L1 signal and the data. In this way, a likelihood that UE 120 does not retransmit data that is not successfully received by BS 110 is reduced. Moreover, based at least in part on retransmitting the data in a next available resource, a delay in retransmission may be reduced relative to another technique where retransmission is delayed until BS 110 requests retransmission.

As indicated above, FIG. 10 is provided as an example. Other examples are possible and may differ from what was described with respect to FIG. 10.

FIG. 11 is a diagram illustrating an example process 1100 performed, for example, by a UE, in accordance with various aspects of the present disclosure. Example process 1100 is an example where a UE (e.g., UE 120) performs URLLC transmission using grant-free resources.

As shown in FIG. 11, in some aspects, process 1100 may include transmitting, on a grant-free resource in an ultra-reliable low-latency communications (URLLC) network, data and a layer 1 (L1) signal for identification of the UE (block 1110). For example, the UE (e.g., using controller/processor 280, transmit processor 264, TX MIMO processor 266, MOD 254, antenna 252, and/or the like) may transmit, on a grant-free resource in an ultra-reliable low-latency communications (URLLC) network, data and a layer 1 (L1) signal for identification of the UE. In this case, the UE may transmit a scheduling request, a scrambled demodulation reference signal, and/or the like as the L1 signal.

As shown in FIG. 11, in some aspects, process 1100 may include monitoring for a reception indication as a response to the L1 signal in a reception period occurring after transmission of the L1 signal on the grant-free resource (block 1120). For example, the UE (e.g., using antenna 252, DEMOD 254, MIMO detector 256, receive processor 258, controller/processor 280, and/or the like) may monitor for a reception indication as a response to the L1 signal in a reception period occurring after transmission of the L1 signal on the grant-free resource.

Process 1100 may include additional aspects, such as any single aspect or any combination of aspects described below and/or in connection with one or more other processes described elsewhere herein.

In some aspects, the UE may start a retransmission timer in connection with transmission of the data and the L1 signal, and wherein the reception period is shorter than an interval defined by the retransmission timer. In some aspects, the reception indication signals to the UE that the UE was identified as transmitting on the grant-free resource. In some aspects, the reception indication is not received in the reception period; and the L1 signal is retransmitted in a next available resource after the reception period based at least in part on the reception indication not being received in the reception period.

In some aspects, the L1 signal is retransmitted prior to expiration of a retransmission timer associated with the transmitting. In some aspects, the reception indication is received in the reception period, the UE monitors for an uplink grant associated with transmitting the data in an interval defined by a retransmission timer. In some aspects, the reception indication is received as the response to the L1 signal before an acknowledgement/negative acknowledgement (ACK/NACK) of the data transmitted on the grant-free resource.

In some aspects, the reception period is a monitoring occasion immediately succeeding transmission of the L1 signal. In some aspects, the reception indication is received in an empty grant, and the L1 signal comprises a scheduling request or a demodulation reference signal. In some aspects, the reception indication is received based at least in part on a network configuration relating to providing the reception indication as the response for a grant-free resource transmission.

Although FIG. 11 shows example blocks of process 1100, in some aspects, process 1100 may include additional blocks, fewer blocks, different blocks, or differently arranged blocks than those depicted in FIG. 11. Additionally, or alternatively, two or more of the blocks of process 1100 may be performed in parallel.

FIG. 12 is a diagram illustrating an example process 1200 performed, for example, by a BS, in accordance with various aspects of the present disclosure. Example process 1200 is an example where a BS (e.g., BS 110) performs URLLC reception using grant-free resources.

As shown in FIG. 12, in some aspects, process 1200 may include receiving, in an ultra-reliable low-latency communications (URLLC) network, a layer 1 (L1) signal on a grant-free resource (block 1210). For example, the BS (e.g., using antenna 234, DEMOD 232, MIMO detector 236, receive processor 238, controller/processor 240, and/or the like) may receive, in an ultra-reliable low-latency communications (URLLC) network, a layer 1 (L1) signal on a grant-free resource.

As shown in FIG. 12, in some aspects, process 1200 may include identifying a user equipment (UE) that transmitted on the grant-free resource based on the L1 signal (block 1220). For example, the BS (e.g., using controller/processor 240 and/or the like) may identify a UE (e.g., UE 120) that transmitted on the grant-free resource based on the L1 signal.

As shown in FIG. 12, in some aspects, process 1200 may include transmitting, to the UE, a reception indication as a response to the L1 signal in a reception period occurring after reception of the L1 signal (block 1230). For example, the BS (e.g., using controller/processor 240, transmit processor 220, TX MIMO processor 230, MOD 232, antenna 234, and/or the like) may transmit, to the UE, a reception indication as a response to the L1 signal in a reception period occurring after reception of the L1 signal.

Process 1200 may include additional aspects, such as any single aspect or any combination of aspects described below and/or in connection with one or more other processes described elsewhere herein.

In some aspects, the reception indication is transmitted as the response to the L1 signal before data decoding of data received on the grant-free resource is completed. In some aspects, the reception indication is transmitted in a next PDCCH occasion following reception of the L1 signal.

In some aspects, the reception indication comprises is transmitted in an empty grant which does not assign uplink resources to the UE, and the L1 signal comprises a scheduling request or a demodulation reference signal. In some aspects, the base station is configured to provide, before receiving the L1 signal, information to configure whether the reception indication is to be provided as the response to the L1 signal. In some aspects, the base station is configured to receive a retransmission of the L1 signal from the UE. In some aspects, the base station is configured to receive from the UE a retransmission of another L1 signal for which an initial transmission is not received.

Although FIG. 12 shows example blocks of process 1200, in some aspects, process 1200 may include additional blocks, fewer blocks, different blocks, or differently arranged blocks than those depicted in FIG. 12. Additionally, or alternatively, two or more of the blocks of process 1200 may be performed in parallel.

The foregoing disclosure provides illustration and description, but is not intended to be exhaustive or to limit the aspects to the precise form disclosed. Modifications and variations are possible in light of the above disclosure or may be acquired from practice of the aspects.

As used herein, the term component is intended to be broadly construed as hardware, firmware, or a combination of hardware and software. As used herein, a processor is implemented in hardware, firmware, or a combination of hardware and software.

Some aspects are described herein in connection with thresholds. As used herein, satisfying a threshold may refer to a value being greater than the threshold, greater than or equal to the threshold, less than the threshold, less than or equal to the threshold, equal to the threshold, not equal to the threshold, and/or the like.

It will be apparent that systems and/or methods, described herein, may be implemented in different forms of hardware, firmware, or a combination of hardware and software. The actual specialized control hardware or software code used to implement these systems and/or methods is not limiting of the aspects. Thus, the operation and behavior of the systems and/or methods were described herein without reference to specific software code—it being understood that software and hardware can be designed to implement the systems and/or methods based, at least in part, on the description herein.

Even though particular combinations of features are recited in the claims and/or disclosed in the specification, these combinations are not intended to limit the disclosure of possible aspects. In fact, many of these features may be combined in ways not specifically recited in the claims and/or disclosed in the specification. Although each dependent claim listed below may directly depend on only one claim, the disclosure of possible aspects includes each dependent claim in combination with every other claim in the claim set. A phrase referring to “at least one of” a list of items refers to any combination of those items, including single members. As an example, “at least one of: a, b, or c” is intended to cover a, b, c, a-b, a-c, b-c, and a-b-c, as well as any combination with multiples of the same element (e.g., a-a, a-a-a, a-a-b, a-a-c, a-b-b, a-c-c, b-b, b-b-b, b-b-c, c-c, and c-c-c or any other ordering of a, b, and c).

No element, act, or instruction used herein should be construed as critical or essential unless explicitly described as such. Also, as used herein, the articles “a” and “an” are intended to include one or more items, and may be used interchangeably with “one or more.” Furthermore, as used herein, the terms “set” and “group” are intended to include one or more items (e.g., related items, unrelated items, a combination of related and unrelated items, etc.), and may be used interchangeably with “one or more.” Where only one item is intended, the term “one” or similar language is used. Also, as used herein, the terms “has,” “have,” “having,” and/or the like are intended to be open-ended terms. Further, the phrase “based on” is intended to mean “based, at least in part, on” unless explicitly stated otherwise. 

What is claimed is:
 1. A method of wireless communications performed by a user equipment (UE), comprising: transmitting, on a grant-free resource in an ultra-reliable low-latency communications (URLLC) network, data and a layer 1 (L1) signal for identification of the UE; and monitoring for a reception indication as a response to the L1 signal in a reception period occurring after transmission of the L1 signal on the grant-free resource.
 2. The method of claim 1, further comprising: starting a retransmission timer in connection with transmission of the data and the L1 signal, wherein the reception period is shorter than an interval defined by the retransmission timer.
 3. The method of claim 1, wherein the reception indication signals to the UE that the UE was identified as transmitting on the grant-free resource.
 4. The method of claim 1, wherein the reception indication is not received in the reception period; and wherein the L1 signal is retransmitted in a next available resource after the reception period based at least in part on the reception indication not being received in the reception period.
 5. The method of claim 4, wherein the L1 signal is retransmitted prior to expiration of a retransmission timer associated with the transmitting.
 6. The method of claim 1, wherein the reception indication is received in the reception period, and wherein the UE monitors for an uplink grant associated with transmitting the data in an interval defined by a retransmission timer.
 7. The method of claim 1, wherein the reception indication is received as the response to the L1 signal before an acknowledgement/negative acknowledgement (ACK/NACK) of the data transmitted on the grant-free resource.
 8. The method of claim 1, wherein the reception period is a monitoring occasion immediately succeeding transmission of the L1 signal.
 9. The method of claim 1, wherein the reception indication is received in an empty grant; and wherein the L1 signal comprises a scheduling request or a demodulation reference signal.
 10. The method of claim 1, wherein the reception indication is received based at least in part on a network configuration relating to providing the reception indication as the response for a grant-free resource transmission.
 11. A method of wireless communications performed by a base station, comprising: receiving, in an ultra-reliable low-latency communications (URLLC) network, a layer 1 (L1) signal on a grant-free resource; identifying a user equipment (UE) that transmitted on the grant-free resource based on the L1 signal; and transmitting, to the UE, a reception indication as a response to the L1 signal in a reception period occurring after reception of the L1 signal.
 12. The method of claim 11, wherein the reception indication is transmitted as the response to the L1 signal before data decoding of data received on the grant-free resource is completed.
 13. The method of claim 11, wherein the reception indication is transmitted in a next PDCCH occasion following reception of the L1 signal.
 14. The method of claim 11, wherein the reception indication comprises an empty grant which does not assign uplink resources to the UE; and wherein the L1 signal comprises a scheduling request or a demodulation reference signal.
 15. The method of claim 11, wherein the base station is configured to provide, before receiving the L1 signal, information to configure whether the reception indication is to be provided as the response to the L1 signal.
 16. The method of claim 11, wherein the base station is configured to receive a retransmission of the L1 signal from the UE.
 17. The method of claim 11, wherein the base station is configured to receive from the UE a retransmission of another L1 signal for which an initial transmission is not received.
 18. A user equipment (UE), comprising: a memory; and one or more processors operatively coupled to the memory, the memory and the one or more processors configured to: transmit, on a grant-free resource in an ultra-reliable low-latency communications (URLLC) network, data and a layer 1 (L1) signal for identification of the UE; and monitor for a reception indication as a response to the L1 signal in a reception period occurring after transmission of the L1 signal on the grant-free resource.
 19. The UE of claim 18, wherein the one or more processors are further configured to: start a retransmission timer in connection with transmission of the data and the L1 signal, wherein the reception period is shorter than an interval defined by the retransmission timer.
 20. The UE of claim 18, wherein the reception indication signals to the UE that the UE was identified as transmitting on the grant-free resource.
 21. The UE of claim 18, wherein the reception indication is not received in the reception period; and wherein the L1 signal is retransmitted in a next available resource after the reception period based at least in part on the reception indication not being received in the reception period.
 22. The UE of claim 21, wherein the L1 signal is retransmitted prior to expiration of a retransmission timer associated with the transmitting.
 23. The UE of claim 18, wherein the reception indication is received in the reception period, and wherein the UE monitors for an uplink grant associated with transmitting the data in an interval defined by a retransmission timer.
 24. The UE of claim 18, wherein the reception indication is received as the response to the L1 signal before an acknowledgement/negative acknowledgement (ACK/NACK) of the data transmitted on the grant-free resource.
 25. The UE of claim 18, wherein the reception period is a monitoring occasion immediately succeeding transmission of the L1 signal.
 26. The UE of claim 18, wherein the reception indication is received in an empty grant; and wherein the L1 signal comprises a scheduling request or a demodulation reference signal.
 27. The UE of claim 18, wherein the reception indication is received based at least in part on a network configuration relating to providing the reception indication as the response for a grant-free resource transmission.
 28. A base station, comprising: a memory; and one or more processors operatively coupled to the memory, the memory and the one or more processors configured to: receive, in an ultra-reliable low-latency communications (URLLC) network, a layer 1 (L1) signal on a grant-free resource; identify a user equipment (UE) that transmitted on the grant-free resource based on the L1 signal; and transmit, to the UE, a reception indication as a response to the L1 signal in a reception period occurring after reception of the L1 signal.
 29. The base station of claim 28, wherein the reception indication is transmitted as the response to the L1 signal before data decoding of data received on the grant-free resource is completed.
 30. The base station of claim 28, wherein the reception indication is transmitted in a next PDCCH occasion following reception of the L1 signal. 